The Monster Within
by AwakeAndAliveSpartan
Summary: When Loki transforms the Avengers into the monster they are dressed as on Halloween, chaos ensues. Will they be able to cure themselves before the chaos takes them over? Or will the curse destroy them? But what happens if one of their own becomes a true,insane monster, threatening to kill them all? Can they fix themselves and stop the monster from destroying everything?
1. Chapter 1

Chapter One

Loud, creepy sounding music boomed throughout Stark Tower." See Thor, this is Halloween." said Stark, waving his hand towards the Halloween-themed tower. It was Halloween, and Stark was throwing a costume party. Stark grinned through his zombie makeup at the Viking-dressed Thor. "This is glorious!" Thor yelled, stuffing another popcorn ball into his mouth and walking away. "Asgardians." Stark grumbled. "Stark, you look like you belong in the Walking Dead!" exclaimed a green colored Barton. "I'll take that as a complement. And you, why are you green?" replied Stark. Barton showed off his muscles. "Hulk smash!" he grinned. Stark shook his head, "Oh right, Hulk." he said, looking at Barton's ripped-up pants and shirt. "Hulk angry!" Barton yelled, stomping off into the crowd. "I swear, I sometimes think something is wrong with him." Stark muttered. Something white caught his eye. "Banner!" Stark exclaimed. Banner had gauze wrapped all around him, only leaving one eye visible. "Hrmph, phhsh, mrrr." said Banner, inaudible. Stark helped Banner make a mouth hole. "Come again?" laughed Stark. "Never let Barton help you with a mummy costume." he stated. "You should've known better than that." grinned Stark. "Yeah, I know." Banner grumbled. Rogers and Romanoff walked up. "What's up Living Dead?" asked Romanoff. "Ha ha, witch. And vampire." joked Stark, looking at Rogers. A crash sounded in the room. "Nat, you may want to keep an eye on Clint." stated Banner. "Crap. Clint, you are really not the Hulk!" she yelled, running after Barton. "Yo Steve, check out Coulson." laughed Stark, pointing at Coulson in the crowd. "Aw man." groaned Rogers. Coulson was dressed exactly like his hero, Captain America. "It looks like you have a boyfriend!" joked Stark. "Shut up." growled Rogers. Romanoff came back, dragging Barton by the arm. "You stay here." she ordered. "Humph." replied the green Hawk. Suddenly, a cold wave washed over them. They shuddered. "Draft, I suppose." stated Stark. "Why is Thor dressed as a Viking when he basically is one?" asked Banner. "I don't know." replied Romanoff. "Who really knows?"

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**Author's Note:** Disclaimer: I don't own the Avengers or any of the characters, Marvel does. Sorry the chapter is so short, I originally wrote this in a notebook, so it looked much longer than it actually is. I promise the chapters will get longer as the story goes on.


	2. Chapter 2

Chapter Two

Stark slowly rose from his bed. "Man, that party hammered me." he groaned. His voice sounded deeper than normal for some reason. He trudged to the bathroom. A look of pure terror washed over him. His zombie makeup was still on, even though he had sworn that he had taken it off the night before. Stark poked his face, a piece of foul-smelling skin fell off. "_! What is this?! Am I really a freaking zombie?!" he yelled. "I'm so glad that Pepper is out of town for a week." he grumbled. A muffled moan sounded from Banner's room. "What the heck?!" It was Banner. Stark ran, as fast as he could, to the hallway. There stood Banner, still covered in gauze. His only visible eye widened at the sight of Zombie-Stark. "What the _ is going on?! Why are we really a mummy and a zombie?!" Banner screeched. "Some freaky spell or something. But what's odd is that these were our costumes last night!" exclaimed Stark. Thor and Rogers lumbered out of their rooms. Their eyes widened at the sight of Stark and Banner. "You know it's November now, right?" asked Rogers. "We aren't playing. This is some kind of magic who-hah going on." said Stark. Rogers frowned and touched his teeth. "_!" he cussed. "Vampire!" Thor laughed, "But why not me?" he asked. "You were basically yourself!" yelled Banner. Barton and Romanoff walked in. "It happened to you too, ha!" laughed Barton, "But not me!" Romanoff snapped, for now she was an actual witch, "Shut up Clint! This doesn't involve you whatsoever!" Barton narrowed his eyes, "Fine, be that way. But don't call me if someone turns into a frog or Banner or Stark loses a limb." he snapped, storming off. Thor frowned, "This has my brother all over it." he said. "You mean that crazy crack-head is still doing his magical spells?!" demanded Stark. "It appears so. It seems that this spell was cast last night. Probably when you were in your dress-up clothing. The spell has seemed to turn you into whatever monster you masqueraded as. But I was immune." Thor explained. Zombie-Stark frowned, "What about Barton though?" he asked. "What was he again?" asked Rogers. "Um, he was…Oh _!" spat Stark. "What?" asked Romanoff. "He was dressed as the Hulk!" exclaimed Stark. "If this magic baloney affected him too, we have a major problem on our hands." Romanoff became nervous, "I think I have already made him mad." she whispered. " He may become like Banner, a time-bomb. We need to find him before it goes off." said Rogers. "Then where is he in my tower?!" demanded Stark. "I don't know. He stormed off very quickly, he may be anywhere in here by now, knowing him." said Romanoff. "And he's very hot-headed. This could be really, really bad." commented Banner. "Then stop snoozing around!" yelled Stark, "We need to find him, fast! Before the clock runs down"

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**Author's Note: **Disclaimer again: Marvel owns the Avengers, not me. Yes, that chapter was short as well. I'm adding in more things to the original as I go along. But I hope you will enjoy the story. PS: It starts to get darker as the story progresses.


	3. Chapter 3

Chapter Three

"Yell at me!" screeched Barton, throwing a piece of lab equipment at the wall of one of Stark's labs. He had wondered in here after Romanoff had snapped at him. "They should be glad that nothing happened to me!" he screamed. "They all look like freaks anyway!" Another piece of equipment was flung at the wall. He suddenly doubled over in rage and agony. "They've….Always….Disliked….Me!" he struggled to growl out. A bright, green glow shone from his eyes. He arched up and let out a monstrous, inhuman noise. His muscles rippled and rapidly expanded. His skin turned a pale green shade. Inhuman growls and roars filled the lab. Then silence filled the room, and a massive figure stood. The figure seemed to be slightly smaller than the Hulk. Paler too. And of course, he looked like Barton. The monstrous Hawkeye threw back his head and let out a thunderous roar.

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The roar echoed through the tower. "_! We're too late!" cussed Stark, in his fastest zombie-run. "Sounds like the lab area." stated Mummy-Banner. "You two stand back." commanded Rogers. "Why?" asked Stark. "With your and Banner's frail, undead condition, he'll rip you apart like a piece of paper." explained Romanoff. Banner and Stark slowed and stopped. A piece of the wall shattered and Hulk-Barton barged through. He towered over him and growled. "He's smaller, and paler." commented Thor, stepping back a couple feet. "Stark, Banner! Stand back! We'll handle him!" yelled Witch-Romanoff, dodging a massive fist. Another fist slammed into Thor. Thor rolled and sent a massive blow to Barton's back with Mjolnir. He fell, angrier than ever. Stark ran into a lab for cover. Rogers sent a fist into Barton's jaw. He roared and swung again, sending Thor into the wall. Romanoff swung herself onto Barton's now-massive neck. She held on tightly, "Clint!" she exclaimed. "It's Nat! Snap out of it!" she yelled. He only roared and flung her to the floor. Stark now appeared, holding what seemed to be a tranquilizer gun. "Get down!" he yelled, sending three needles into Barton. He staggered and fell to the ground with a thud. His transformation back started to occur with a groan. "Rogers, get him." said Stark, pointing to the now almost naked Barton. "We'll take him to my Hulk-proof cell."

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**Author's Note: **Disclaimer: I don't own the Avengers, Marvel does. Sorry, this chapter was a little shorter. These chapters will vary in length. This was mostly an action chapter. PS: Agents of SHIELD characters will be in the story soon


	4. Chapter 4

Chapter Four

Zombie-Stark stood, looking at the unconscious Barton in the cell next to him. He turned to Thor, who was in the room beside him and everyone else was elsewhere, "Thor, can you find your brother to fix thtis crap?" he asked. "I can try, he is still in Asgard. So he couldn't be that hard to find." Thor replied. He vanished in a flash of light. Stark frowned and turned on his radio. He frowned at the now ironic song that was playing, but he didn't turn it off. '_For this is not your funeral, wake up, wake up, wake up, wake up the zombie. Wake up the zombie!' _the song sung. "I wish it was that easy." He said quietly to himself. He looked at the still unconscious Barton. '_You started forgetting who you really are. I'm getting kind of worried, you've been gone for so long. And how, is your heart still beating? Where did the human go?...'_ Stark tuned the song out and walked out of the room to somewhere else.

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Barton woke with a sudden start. He jumped to see that he was imprisoned for some reason. "Why am I in Stark's Hulk cell?!" he yelled to absolutely no one. He frowned and thought for a minute. He growled when he remembered what had happened to him. "They distrust me this bad?! They stick me in here after one little time?!" he screeched. He pounded on the glass, looking for a way out. He noticed a radio playing somewhere outside of the cell. '_Someone save me from this, make it end. I feel it deep within, it's just beneath the skin. I must confess that I feel like a monster.'_ He slammed his fist against the probably four-inch thick glass. "How _ appropriate!" he screeched. A light started flashing on the ceiling of the cell. A camera. It had probably been activated in response to movement within the cell. Barton turned to face it and snarled at it. '_It's hiding in the dark..'_ "They can die for all I care!" '_There's no escape for me. It wants my soul, it wants my heart…'_ " Maybe they'll go crazy! Maybe Stark and Banner will decay and fall apart!" '_Maybe it's inside of me, stop this monster.' _The radio died, leaving one line of the song to echo eerily throughout the cell, _'Stop this monster.'_

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**_Author's Note:_**Disclaimer: I still don't own the Avengers, Marvel does. I don't own the songs used partially in this short chapter. The first one is 'Zombie' by We As Human and the second one is 'Monster' by Skillet. The songs belong to their rightful owners. Yes, another short chapter. I don't write that much because I'm not very descriptive with writing. It's still gonna get darker from here. Next chapter Hawkeye starts losing his mind and goes insane. Agents of SHIELD will come in in about two chapters.


	5. Chapter 5

Chapter Five

A bright light shone in front of Stark, Banner, Romanoff, and Rogers. The light died down to reveal Thor holding his brother Loki in a tight death grip by his collar. Thor threw Loki to the floor of the tower, "Undo your demonic spell, Loki!" he commanded in a fierce growl. Loki got up from the floor and grinned at the sight of the monstrous Avengers. "Heh, heh." he chuckled. "Alright then, I was just getting into what you Midgardians call the 'Halloween Spirit'." He laughed again and snapped his fingers. A harsh glow settled over the Avengers. When it seemed to die down, they were surprised to see that they were normal again. Stark stormed over to Loki and looked him straight in the eye, "What about Barton?" he growled. Loki's grin returned, "Ah, the Archer. There's nothing I can do for him." he replied in an obviously fake sympathetic tone. Romanoff's eyes narrowed, "What do you mean?" she asked in a low voice. "You see, your so-called Gamma Radiation runs strong through his blood. That is something that I cannot help. His current state remains exactly the same. Nothing I can do." His smile grew even more, "There is simply nothing I can do." Thor grabbed Loki by the collar again, "Brother!" he growled. Loki only smiled again and disappeared in a puff of black colored smoke. Stark looked around the room and snarled, "He's _ gone!" he exclaimed. Rogers frowned, "Stark, don't worry about Loki. He's not the problem at all now. We have to focus solely on Barton. He's our top priority as of right now." he explained. "What I have to worry about is two Gamma-irradiated men in my _ tower!" Stark snapped back. "Tony, calm down." Banner said calmly. "We can find a way to help Clint, I hope." Romanoff's eyes scanned the three Avengers, "Our only option now is to go get Clint and see if there is anything at all we can do." she explained. Stark calmed down a little, "I guess you are right. The only thing we can do is see if we can do anything at all to help him. Or at least stop him from killing us all."

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Barton sat in a corner of the cell in a somewhat psychotic daze. Well, psychotic was the least of it. His body shook slowly as monstrous growls, roars, and rumbles filled his head. He rocked back and forth murmuring crazy rambles to himself. "They'll just kill you. They hate you. Monster, demon, beast, SHIELD, experimentations, lock-up, death." His mad rambles went on and on. He was way too out of it to see the other five Avengers walk into the room and surround the cell. "Clint?" Romanoff called. There was no response. She tried again, "Clint? Are you alright?" Barton's head suddenly whipped around to face them. Sweat glistened on his face. A mad, psychotic look was drilled into his normally hardened eyes. Worry swept over the Avengers like a flood. "Clint, stop playing." Stark stated, anxiety weighing in his stomach like a rock. "I don't think he's playing Tony." Banner replied. A troubled, raspy voice escaped from Barton's lips, "He's everywhere, darkness consumes. Titan is here and there, everywhere. Madness, insanity, destroys, kills, and burns." A look of pure agony fill his normally greenish-brown eyes. Stark whistled, "I think he's lost it." Banner frowned, "This doesn't make sense. Why is he gone insane?" he asked. "He probably doesn't have the strongest mind." Thor stated," That is why his was prone to Loki's control. This beast, is ravaging his mind." Rogers frowned as well, "Then who's 'Titan'?" he asked. "Maybe his name for the beast." Stark replied. Romanoff suddenly made her way towards the door of the cell. "Nat, what the heck are you doing?" Stark asked, making his way to stop her. She put her hand to stop him. "I'm going in." she replied. "I'm going to make sense of this insanity."

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**Author's Note: **Again. I don't own the Avengers. Marvel does. Yes, I made this chapter a little longer. I hope it helps. Coulson will come in the next chapter, so there you go with Coulson. If you are wondering why the other Avengers' transformations didn't last long, it was Loki's plan. He knew Thor would automatically know it was him and quickly get him to fix it. It was Loki's plan to throw the Avengers off guard with their own transformations, so Hawkeye's condition would get worse because they couldn't do anything for him. Loki could've helped Hawkeye, but he lied saying Gamma Radiation was out of his control. I hope you enjoy!


	6. Chapter 6

**Chapter Six**

"What do you mean that Barton has gone insane!?" Coulson's frantic voice filled Roger's earpiece. "We'll explain later." Rogers replied. "But bring medical help ASAP." he said frantically. "Ok." Coulson replied suspiciously. "I'll bring help. Coulson out." Roger frowned. "You better hurry.

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Romanoff slowly walked into the cell. "Clint?" she asked. A pained whimper came in reply. "It's me, Nat. Steve has called for help. Coulson's coming to help." she slowly reassured. He jerked up, "No! No Coulson! No SHIELD!" he screeched, striking Romanoff in the side with his arm. "Nat, get out of there. Now." Stark commanded. She didn't listen. She gripped Barton by the arms "Listen please." She spoke slowly to him. A wail of pain escaped his lips and he stiffened. He closed his eyes in pain. "Titan." he whimpered. Romanoff frowned. "Clint, who's Titan?" she asked. His eyes suddenly snapped open. Romanoff let go of Barton to see that his eyes had turned a sickly green shade. He fell to the ground in agony. "_!" She bolted towards the door. The door had closed and locked itself. She pounded on the glass. "Stark! Open this _ thing!" she screamed. "I'm trying!" he exclaimed. "The locks are jammed!" Romanoff froze in terror as an inhuman noise sounded behind her. She turned her head ever so slowly toward the noise. She realized it was way too late. Barton lay thrashing on the floor. Muscles expanding and skin turning.

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Coulson landed the small transport jet onto the helipad of Stark Tower, and stepped out onto the concrete. Jarvis' voice sounded from an intercom, "Good evening Agent Coulson. I suggest waiting, Mr. Stark and the other Avengers are tied up at the moment." Coulson ignored this warning and kept walking into the tower. "I can handle it." he grumbled. He walked in search of wherever Rogers had called him from. A sudden roar echoed through the tower's hallways. Coulson quickened his pace, 'Was that Banner?' he thought. The roar sounded again. 'No, not as deep.' He quickened his pace even more, headed towards the origin of the monstrous roar. 'What's going on here?'

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**Author's Note: **I don't own the Avengers, Marvel does. Yes, I know, short chapter. Mostly introducing Coulson into the storyline, and revealing Hawkeye's beast's name. Titan. Again, chapters will vary in length. Please be patient with them. I originally wrote this story in a notebook, it looked much longer. PS: **_Agents of SHIELD_** coming into next chapter!


	7. Chapter 7

**Chapter Seven**

Thor swung his hammer Mjolnir into the door of the cell, breaking it into millions of pieces. Romanoff darted out, falling onto the floor in a panic. Stark was already armored in his Iron Man suit. The transformed Barton leapt out of the cell, sending Thor into the ground. "That must be Titan…" Romanoff whispered, shaking. "What?!" The saddened shout came from the doorway. Stark turned to see Coulson standing in the doorway, gun in hand. "What is that?!" Coulson exclaimed, pointing at the massive Titan. "How do we put this," Rogers replied, dodging a massive fist. "That's, uh, Barton." Coulson gripped his handgun even harder. "What?!" he gaped. "We'll explain later." Stark replied, a mini-gun extending from his armor on his arm. He fired four needles from it. The needles hit Titan square in the back. The beast roared and collapsed to the ground with a massive thud. The transformation back to Barton began with a groan and ended with another. "Thor, get him and go with Coulson." Stark ordered, pointing at the unconscious, half-naked Barton on the ground. Thor agreed and hefted Barton up and over his shoulder and followed Coulson to his jet. "I'll go." Romanoff said, starting towards the door. Coulson called out from the other room, "No, you all are going. I need a massive explanation."

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Later on, the group arrived at the SHIELD Bus. They went inside, lugging Barton to another containment cell. Agent Ward saw them, "What happened to the great Hawk now?" he snickered. "Ward! This is no time for your jokes!" Coulson snapped. Agents Fitz and Simmons walked into the containment lab. "Why is Agent Barton in our containment cell?" Simmons asked. "Ah, he's all….Gammafied." Stark replied, looking for the best answer. "Gamma, as in Gamma Radiation? As in the Hulk?" Fitz replied. "Now, I need an answer. What the heck happened to him?" Coulson asked. Stark told him the whole story. "Loki's an idiot." Skye stated, walking into the room. "Skye, this is none of your business." Ward retorted. "And why can't it be? Aren't I technically a part of SHIELD?" she asked. Coulson sighed, "Leave it. There are other matters." He looked around, "Fitz, Simmons. You two work with Stark and Banner." Fitz frowned, "To do what?" he asked. "To try and help Barton." Coulson replied. Fitz frowned again and looked at the imprisoned Barton, "But how do we help a Gamma-filled man?"

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**Author's Note: **Again, I don't own the Avengers or Agents of SHIELD, Marvel does. Next chapter, Hawkeye goes even more insane. One moment he's vegetable-like and then he's normal, but his mind and thoughts are distorted by Titan and Loki's dark magic. So, he still says some crazy things (That's next chapter.). I hope you like.


	8. Chapter 8

**Chapter Eight**

Barton groaned and peeled his eyes open. The harsh light burned his eyes. He noticed that he was wearing a white t-shirt, black pants, but not shoes or socks. 'Where am I?' he thought. He looked around his new cell, 'Great another one.' He thought again. He noticed lab equipment outside the cell and a small, curly-haired man sitting at a computer. The man noticed that Barton was awake and scampered off. 'SHIELD? Great.' The man returned with a woman and who seemed to be Stark and Banner. "Clint, at least you're awake and don't seem to be in some kind of psychotic state." Stark commented. "And hello to you too." Barton shot back. "You trust me so much that I get my very own cell!" he growled. "And what is all this lab crap for?!" Banner frowned, "We're working with lab agents Fitz and Simmons." he said, pointing at the two agents. "Who are they?" Barton growled. "We're a part of Agent Coulson's team." Fitz replied. Barton noticed that Fitz had a thick Irish accent. "Coulson. So SHIELD's in this?" he snarled. "No. It's just Coulson's team. We've asked Coulson to keep this from Fury." Stark replied. Barton shuffled his bare feet, "And how do you expect to cure me from something Banner can't even cure himself from?!" he screamed. Banner gulped. He _was _right. He couldn't even cure himself from his Gamma monster. How could they cure Barton? "That is something we'll work on, I promise." Banner replied. Barton hissed and turned to the single cell bed. "Containing me, like I'm a virus. A biohazard to you all. How does that help?" he hissed. "Clint." Stark began. "Enough!" he screamed. "That is what you think I am. Like I am the beginning of some kind of zombie apocalypse." That part was directed towards Stark. "Keeping me contained will do nothing what so ever." he hissed. Fitz and Simmons backed up. "Clint, you're mental. Titan or whoever is messing with your brain." Stark stated, frowning. A psychotic smile formed on Barton's face. "No, this is all me." he hissed. "And soon it will be time to ride a circus for a psycho."

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**Author's Note:** Again, I don't own the Avengers or Agents of SHIELD, Marvel does. A short chapter again. I hope to write a story later on that is much, much longer. The part where Hawkeye is wearing only a white shirt and black pants is a poke towards the music video for '_**Monster'** _by Skillet. In the video the lead singer plays a man who wakes up in a biohazard unit wearing the same outfit and he has to fight off doctors that are experimenting on him and run from soldiers for his freedom. And where it says '_**it's time to ride a circus for a psycho'** _, that is a line from the Skillet song _**'Circus for a Psycho.'** _Both songs belong to them. I hope you enjoy!


	9. Chapter 9

**Chapter Nine**

A lone Fitz walked into the lab to turn off a piece of equipment he had forgotten to turn off earlier. The lab was dark and quiet. Barton's crazed words still rung in Fitz's head, 'And it's time to ride a circus for a psycho.'

'What the heck is a circus for a psycho anyway?' he thought to himself. Fitz turned off the machine but froze to find a cold, hard knife pressed up against his throat. He let out a silent scream to see that it was the psychotic Barton, somehow out of his cell.

Barton smiled widely and gagged and bound Fitz up with rope and duct tape. He threw Fitz to the ground and dashed madly out of the room to who knows where. Fitz lay on the ground in embarrassment and fright. He let out a muffled scream.

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"Where is Fitz? He should be back by now." May asked. "I think he just went to turn off something in the lab." Simmons replied. Coulson sighed, "Simmons, Ward, Skye, come with me. May, go check the Bus systems. Something isn't right here.

Stark frowned, "What about me and Banner?" he asked. Coulson looked at the two scientists and frowned. "Stay here. There's no use for you getting hurt." He eyed Banner, "Especially you.

Coulson's small group walked into the dark lab. Ward flipped the lights on. "Oh my! Leo!" Simmons screamed at the sight of the bound-up agent. Coulson freed him from the rope and ripped the tape off of his mouth.

"What happened?" Coulson asked. Fitz sat up, rubbing his very raw lip. "It's Barton, he's gone." he stammered. Their heads snapped to the now-empty cell. "How?!" Skye exclaimed. Suddenly a muffled shout sounded from what sounded like the Bus's cockpit.

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**Author's Note: **I don't own the Avengers or Agents of SHIELD, Marvel does. Yes, very short chapter. Also it's now in paragraph form thanks to a 'lovely' review. It wasn't in paragraph form originally when I wrote it, so I didn't bother to fix it. But since that 'nice' review, I changed it. I guess it is now easier to read. I wont be updating this story as often because I am now working on _**Wolf's Blood,**_my other Avengers fanfic. It takes me awhile to type each chapter of that story, but I promised I'll try to update this one more. ~AwakeAndAliveSpartan.


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